Geographic Range

Eastern small-footed bats are native to the United States and Canada. Despite their wide distribution, they are one of the rarest bats in North America. They range from as far north as Ontario, to as far south as Georgia, and as far west as Oklahoma. This species has been documented in the Ozark Mountains in Arkansas, Missouri and Oklahoma. They are found in the Appalachian mountains north to southeastern Canada and the New England states. In the southern parts of its range, eastern small-footed bats are limited to caves and rocky outcrops in Virginia, North Carolina, South Carolina, Tennessee, Kentucky, Alabama, and northern Georgia. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Best and Jennings, 1997; Chapman, 2007; Linzey, 1998)

Physical Description

Eastern small-footed bats are the smallest of the Myotis genus ranging from 3.5 to 6 grams with a length of 75 to 85 mm and a wing span of 210 to 250 mm. They derive their common name from the fact that they are the only member of the Myotis genus (in Virginia) with feet measuring less than 9 mm. The sexes are similar in coloration and size. Their fur is black at the root with brown shiny tips; this gives them their glossy yellowish-brown appearance. Their underside is a dull grayish-brown. The completely black face mask is its most unique feature. They also have black ears, wings, and interfemoral membranes (a stretch of membrane that extends between the legs to the tail). Females have two mammae (or milk glands). They have a strongly keeled calcar (a protruding piece of cartilage on the hind leg to support the intefemoral membrance) and a pointed tragus (a fleshy projection which extends from the base of the ear) of about 9 mm in length.
Their skulls are relatively flat, short, and fragile. Their dental formula is: incisors 2/3, canines 1/1, premolars 3/3, and molars 3/3. Their foreheads slope gradually away from the rostrum lacking the typical prominent forehead of most Myotis species. Their ears are erect and broad at the base and their noses are blunt. Their tails extend beyond the interfemoral membrane. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Best and Jennings, 1997; Chapman, 2007)

Reproduction

Swarming, which is important for mate selection, breeding, and hibernacula selection, occurs from late summer through early fall. Eastern small-footed bats are polygynandrous, so both males and females have many mates. (Best and Jennings, 1997; Johnson and Gates, 2007)

In the late summer through early fall, many eastern small-footed bats gather together in the same spot. This is important for breeding and for choosing locations to hibernate. Both males and females have multiple mates. (Best and Jennings, 1997; Johnson and Gates, 2007)

Maternity colonies have been observed in New Hampshire, Kentucky, North Carolina, South Carolina, and Ontario. These colonies ranged from a 12 to 33 individuals and the roost locations were diverse. Thirteen individuals were found in rock crevices, 20 in guardrail crevices on a concrete bridge, 12 behind a shed door, and others in wood piles and picnic shelters. Little is known about their breeding behavior. However, one study found a maternity colony in an abandoned cabin in North Carolina. This colony consisted of 33 individuals: 22 adult females, 1 non-reproductive adult male, 3 juvenile males, and 7 juvenile females. Female eastern small-footed bats typically have one offspring per year between May and July. Sperm is stored throughout hibernation, where the female is in sub-estrus, from mid-November to March. Mating has also been documented during the winter if a male and a female are aroused from hibernation at the same time. This is when the female releases an egg and delayed fertilization occurs. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Best and Jennings, 1997; Chapman, 2007; O'Keefe and LaVoie, 2011; Wimsatt, 1945)

Only females care for newborns. They go on foraging trips for food, feed, protect, and teach the young. Mothers leave the newborn soon after birth to look for food. Weaning time is not known. (Best and Jennings, 1997; Wimsatt, 1945)

Lifespan/Longevity

Eastern small-footed bats are estimated to live 6 to 12 years in the wild. This is affected by predation, habitat availability, and exposure to parasites or fungi. The maximum recorded lifespan in captivity was 12 years. In northern regions of their geographic range, males have a higher rate of survival (75%) than females (42%). This could be due to the higher demand on females during reproduction. Maternity colonies are not always present, so there is a large increase in energy output for thermoregulation of both pregnant and lactating females compared to those involved in clustering behaviors. ("Conservation Assessments for Five Forest Bats Species in the Eastern United States", 2006; Best and Jennings, 1997; Hitchcock, et al., 1984)

Eastern small-footed bats live about 6 to 12 years in the wild. This depends on predators, habitat availability, and parasites or fungi. In captivity, the maximum recorded lifespan is 12 years. In northern parts of their range, males are more likely to survive than females. The survival rate for males is 75% and the survival rate for females is 42%. This might be because females have to use more energy during the reproduction process. Females who are pregnant or nursing also use more energy to stay warm if they aren't in a maternity colony. ("Conservation Assessments for Five Forest Bats Species in the Eastern United States", 2006; Best and Jennings, 1997; Hitchcock, et al., 1984)

Behavior

Eastern small-footed bats are nocturnal, roosting during the day and active at night. During the summer, they leave their roosting site around dusk and they fly in and out of caves and through open fields. Their flying height varies from 0.3 to 6.0 meters. In flight, their unusually slow and fluttering motion makes them easily distinguishable from other small bats. They have a very strong homing instinct, returning to the same cave to hibernate even if placed in a different location. They do not migrate but change roosting locations within the same general area. They typically switch roosts daily unless weather prohibits foraging. This frequent relocation requires an abundance of adequate roosting locations within the home range. Males and females have different criteria for roosting selection and these preferences change during the reproductive season, such as the desire by females for roosts with more solar exposure. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Best and Jennings, 1997; Chapman, 2007)

Eastern small-footed bats hibernate during the winter. Within their range, they are the last to hibernate in mid-November and the first species to rise in March. Although they have been observed hibernating in groups, they more often hibernate alone. They hibernate horizontally rather than vertically and sometimes hibernate on cave floors. Their small size allows them to squeeze into small cracks and crevices which provide protection from predators. They prefer to hibernate at the mouths of caves and are often found in caves less than 150 meters long. During torpor, the body's temperature drops to between 1 to 2 degrees Celsius more than the hibernaculum, so they are able to withstand temperatures below freezing. Compared to normal energy output this drop in body temperature decreases their metabolic rate by 95%. They rise from torpor at -9 degrees Celsius. They wake from torpor more often than co-hibernating species, predisposing them to quick depletion of winter energy reserves. This increase awakening from torpor is hypothesized to support immune function despite the estimation that these arousals account for 84% of winter energy output. Between December and April the total body mass lost is around 16%. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Best and Jennings, 1997; Chapman, 2007)

Home Range

Eastern small-footed bats have been recorded moving a maximum of 1.1 km within their home range. (Best and Jennings, 1997)

Communication and Perception

Eastern small-footed bats use echolocation to locate prey, typical among insectivores. Search-phase call is first used to locate an insect. While in pursuit, an approach-phase call is emitted. Immediately before consuming prey, they emit a terminal-phase call or feeding buzz. Both the approach-phase (pre-buzz call) and the terminal-phase (buzz call) are used to determine a range on the prey and maintain the location of the prey item. In one study the duration of search-phase calls were 2.8 ms and other studies have recorded calls as long as 5 ms. The minimum frequency is 46.1 KHz and the maximum frequency is 84.5 KHz. (Chapman, 2007; Murray, et al., 2001; Parsons, et al., 1997)

Food Habits

Eastern small-footed bats are insectivores, specializing in nocturnal flying insects while staying 1 to 3 meters off the ground. Prey include beetles, mosquito, moths, and flies. Occasionally they feed on ants as well. One study of fecal samples during fall swarming found 7 orders, 1 superfamily, and 9 families of insects. The insects were very diverse but moths were consumed most abundantly. When foraging, they fly slowly and often feed over water where nocturnal insects are abundant and sometimes fill their stomach within an hour of the start of their foraging bout. They have also been observed feeding in dense forested areas using a gleaning strategy, which is described as eating insects from plants, rocks, or other surfaces. This type of feeding is considered the most efficient for bats with long-wing loading. Eastern small-footed bats have short, broad wings with rounded wingtips to that improve maneuverability in dense vegetation. ("Conservation Assessments for Five Forest Bats Species in the Eastern United States", 2006; "Notes on Foraging Activity of Female Myotis leibii in Maryland", 2009; Johnson and Gates, 2007; Norberg and Rayner, 1987)

Ecosystem Roles

Eastern small footed bats host the following ectoparasites: mites (Androlaelaps casalis and Cryptonyssus desultorius), chiggers (Leptotrombidium myotis), and ticks (Ornithodorus kelleyi). Females in maternity colonies have an increased probability of exposure to ectoparasites. Females in northern regions of the United States are more likely to carry the Trypanosoma infection originating from the bat bug, Cimex brevis. These bat bugs are common in maternity colonies in Ontario. (Gikas, et al., 2011; Hitchcock, et al., 1984; Timpone, et al., 2011)

Economic Importance for Humans: Negative

Bats are noted carriers of rabies, which results in a nearly 100% fatality rate if not detected on time. Five out of 45 species of bats has been recorded transmitting rabies to humans in the United States, one of which is suspected to be the eastern small-footed bat. Eastern small-footed bats might also carry Histoplasmosis, a disease caused by the fungus Histoplasma capsulatum. This presents itself with flu-like symptoms and disappears with antifungals and sometimes without need for any treatment. Eastern small-footed bats might also be considered a nuisance because they roost in human structures. ("Current Status and Conservation Strategy for the Eastern Small-footed Myotis", 2001; Best and Jennings, 1997)

Negative Impacts

injures humans

carries human disease

Conservation Status

In 2009, eastern small-footed bats were placed on many conservation lists. In Alabama, Arkansas, Massachusetts, Maryland, Maine, New Hampshire, New Jersey, Oklahoma, Pennsylvania, West Virginia, Virginia, and Vermont they are listed as "critically imperiled." In Georgia, Kentucky, North Carolina, and New York, they are listed as "imperiled." In Connecticut, Massachusetts, Maryland, Missouri, North Carolina, New Jersey, New York, Ohio, Oklahoma, Tennessee, Virginia, West Virginia, and Georgia they are listed as a "species of special concern." In Pennsylvania and Vermont they are listed as "threatened," and are endangered statewide in New Hampshire. On a federal level, they are listed as a species of special concern and are under review by the Endangered Species Act. The state of Michigan gives them no special status and the IUCN Red List lists them as least concern with a stable population trend. They are threatened by human activities because of their reliance on forests for foraging. Activities such as logging, wind turbines, agricultural and urban development contribute to foraging habitat destruction. Oil, gas, and mineral development can destroy roosting sites and contaminents can leak into local streams. ("Federal register notice of a 90-day finding for Eastern Small-footed bat and Northern Long-eared bat", 2011; Terwilliger, 1991)

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. (Cryan, 2010; National Park Service, Wildlife Health Center, 2012)

Other Comments

Eastern small-footed bats became a larger focus for research after fossils were discovered in the Cumberland Cave in Maryland in 1972 and Big Bone Cave in Tennessee in 1975. Species which are closely related were discovered in 1908 in caves in Arkansas from the middle to late Pleistocene. Myotis lebii was previously thought to be a subspecies of Myotis cililabrum, which inhabits areas of the western United States. Genetic analysis isolated M. leibii to its current range and determined that it was a separate species. (Best and Jennings, 1997; Linzey, 1998)

A 1979 study estimated that just 15 percent of all Myotis individuals in late-summer in Virginia caves are Myotis leibii. It is unclear if this is a true indication of their rarity or if they are often overlooked due to their concealed roosting sites within caves. (Best and Jennings, 1997; Linzey, 1998)

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

United States Department of Agriculture. Conservation Assessments for Five Forest Bats Species in the Eastern United States. NC-260. Washington, D.C.: USDA Forest Service. 2006.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.